1. Technical Field
The present invention relates to an electrophoretic particle, a manufacturing method of an electrophoretic particle, electrophoretic dispersed liquid, an electrophoretic sheet, an electrophoretic apparatus, and electronic equipment.
2. Related Art
Generally, it has been known that microparticles move (migrate) in liquid due to coulomb force if an electric field is made to act on a dispersed system obtained by dispersing the microparticles in liquid. This phenomenon is called electrophoresis, and in recent years an electrophoretic display apparatus which displays desired information (image) by using the electrophoresis has attracted attention as a new type of display apparatus.
This electrophoretic display apparatus has a characteristic that the apparatus is provided with a display memory property in a state where voltage application is stopped and a wide viewing angle property, a characteristic that the apparatus can perform high-contrast display with low power consumption, and the like.
In addition, the electrophoretic display apparatus also has a characteristic that display thereof is easy on eyes as compared with light emitting display devices such as a cathode-ray tube display since the electrophoretic display apparatus is a non-light-emitting type device.
As such an electrophoretic display device, a device which is provided with dispersion of electrophoretic particles in solvent as electrophoretic dispersed liquid which is arranged between a pair of substrates with electrodes has been known.
As such electrophoretic dispersed liquid with the above configuration, liquid including positively-charged particles and negatively-charged particles, and non-charged particles as necessary, as the electrophoretic particles is used, and desired information (image) can be thus displayed by applying voltage between the pair of substrates (electrodes).
Here, electrophoretic particles which are provided with covering layers in which polymer molecules are coupled to base particles are generally used as the electrophoretic particles, and with such a configuration including the covering layers (polymer molecules), it is possible to disperse and charge the electrophoretic particles in the electrophoretic dispersed liquid.
An electrophoretic particle with such a configuration is manufactured by using atom transfer radical polymerization (ATRP) as follows.
That is, the electrophoretic particle is manufactured by preparing a base particle, a linking polymerization initiator containing a polymerization initiation group to the surface of the base particle, then forming a polymerization part at which a monomer has been polymerized in living radical polymerization from the polymerization initiation group as a starting point, and providing a polymer molecule (polymer) with characteristics such as an electrification property and a dispersion property (see JP-A-2007-225732, for example).
However, according to the electrophoretic particle manufactured by using such ATRP, the polymer molecule is coupled to the base particle only at one end. Therefore, the polymer molecule is separated from the base particles from the coupling part, at which one end of the polymer molecule and the base particle has been coupled to each other, as a starting point, due to a physical influence of collision between electrophoretic particles resulted from vibration or due to a chemical influence originated from solvent in which the electrophoretic particles are dispersed in the course of manufacturing the electrophoretic apparatus or in the process of using the electrophoretic apparatus. As a result, there is a problem that variations occur in the electrification property, the dispersion property, and the like among the plurality of electrophoretic particles contained in the electrophoretic dispersed liquid when the electrophoretic apparatus is manufactured and used.